The Role of Vertical Transmission of Dengue Virus among Field-Captured Aedes aegypti and Aedes albopictus Mosquitoes in Peshawar, Khyber Pakhtunkhwa, Pakistan

Despite the fact that dengue is one of the major public health threats in Pakistan causing severe outbreaks since 2005, the molecular epidemiology in mosquito (dengue vectors) is limited. Here, we investigated the vertical transmission of dengue virus (DENV) in the Aedes mosquitoes and its (DENV) transmission through other factors mainly tyres trade. DENV was detected in Aedes aegypti (57%) and Aedes albopictus (43%) adults (n=1050) and larvae (n=550). The samples were collected from four (Shuba Bazaar, Tarnab Farm, Wazir Bagh and Hayat Abad) dengue suspected locations of district Peshawar, Khyber Pakhtunkhwa (KPK), Pakistan. A semi-nested multiplex PCR was used to amplify the cDNA of the four dengue serotypes. Six out of 35 (17.14%) adult mosquito pools were found positive for dengue virus with type-2 (77.77 %) and type-3 (11.11 %) while a single (11.11%) pool of concurrent infection with type 2 & 3 was also detected. The adult Ae. aegypti belonging to Shuba Bazaar showed 33% positivity for DENV with minimum infection rate (MIR) 11.1 while that of Wazir Bagh showed 16.67% positivity with MIR 5.5. Similarly, the Ae. albopictus of Shuba Bazaar resulted in 22.22% positivity with MIR. 7.4. The pooled larvae showed 3 (17.64%) positive out of 17, the pooled Ae. aegypti larvae from Shuba Bazaar resulted in 40% positivity (MIR-13.3) while the Ae. albopictus showed 33% positivity (MIR=11.1). These results indicated the vertical mode of dengue virus transmission in Aedes, highest DENV positivity was observed in mosquitoes (adults and larvae) collected from tyres in Shuba Bazaar. The disease burden in Pakistan is critical requiring large-scale molecular epidemiology and entomological surveillance. Moreover, transportation of mosquitoes via tyre trade necessitates more conservative mosquitoes control strategies in Pakistan especially in the unrestricted transport of tyres from southern part of the country to the northern parts.